I am wrong...it is not 3600...it is as you say...my mistake
If you can reach a little under 7 knots at WOT of 3200 rpm in calm water, you have the right size prop. Typically this would be about a 15X8 for 2 blades.
Cruising range is anywhere from 2100-2600 rpm. There is usually a sweet spot where increased rpm's don't give much of a speed increase, so you may find 2200 rpm's provides a nice balance of speed, fuel efficiency, and lack of vibration. I'm happy at 5.2 knots, depending upon wind and wave direction, full water tanks, etc.
You should determine what is on the shaft now, and make sure you have enough cushion to push you to max hull speed.
-Garrett